1. Field of the Invention
The present invention relates to an image data decoding apparatus and a method, and more particularly to an apparatus and a method effective to be applied to an image processing apparatus such as a copying apparatus, a printing apparatus and an image reading apparatus.
2. Description of the Related Art
Since image information becomes large capacity, the image information is usually used in a manner of compression and storage thereof. In addition, in the field of a copying machine and a printer, the image information has been becoming larger in capacity than 1,200 dpi/2,400 dpi, etc., so as to output characters, etc., with high-definition.
Compression techniques for processing such large-capacity data are disclosed by the following documents.
The technique disclosed by the document 1 (Jpn. Pat. Appln. KOKAI Publication No. 11-312173) can store a low-resolution image with a reduced resolution of an original image in addition to the original image. This technique utilizes the low-resolution image instead of the original image in image retrieval, etc., to make a large-capacity image easy to be processed.
The method disclosed by the document 2 (Jpn. Pat. Appln. KOKAI Publication No. 06-22289) is a technique for hierarchically encoding and decoding a moving image in relation to a resolution. Here, the method improves an encoding efficiency and also makes data with an arbitrary resolution possible to be processed by using the low-resolution image in high-resolution image compression.
In the document 3 (Jpn. Pat. Appln. KOKAI Publishing No. 2003-338934), an image in which character parts are extracted from an original image and an image in which a character area is removed from the original image are created. The character area is digitized to conduct MMR compression processing, and the image in which the character area is removed from the original image is resolution-converted to be compressed in a JPEG method and efficiently compressed.
The document 4 (previous U.S. patent application Ser. No. 11/019,986) is the invention previously applied by the inventor of the present invention and the technique in the document 4 achieves a high compression by performing lossless/lossy mixed encoding to a high-definition image of the printer or the like.